In a UMTS (Universal Mobile Telecommunications System) network, for the purposes of further increasing data rates, providing low delay and so on, long-term evolution (LTE) has been under study (see Non Patent Literature 1). In LTE, as multi access schemes, an OFDMA (Orthogonal Frequency Division Multiple Access) based scheme is used in the downlink and an SC-FDMA (Single Carrier Frequency Division Multiple Access) based scheme is used in the uplink.
In the LTE system, signals to be transmitted on the uplink are mapped to appropriate radio resources and transmitted from a user terminal to a radio base station apparatus. In this case, user data is assigned to a PUSCH (Physical Uplink Shared CHannel). As for control information, when it is transmitted together with user data, it is assigned to the PUSCH and when it is transmitted alone, it is assigned to a PUCCH (Physical Uplink Control CHannel). The control information to be transmitted on this uplink includes a retransmission response signal (ACK/NACK) for a PDSCH (Physical Downlink Shared CHannel) signal, a scheduling request, channel state information (CSI) and so on. The CSI includes channel quality information (CQI), precoding matrix indicator (PMI) and rank indicator (RI) information.
The channel state information (reporting) is such as reports CQI/PMI/RI and is performed periodically or aperiodically. Triggering of aperiodic channel state information (Aperiodic CQI/PMI/RI Reporting) to give a transmission opportunity (trigger) with any timing is included in an uplink scheduling grant (DCI format 0). Therefore, the user terminal performs aperiodic reporting of CSI (CQI/PMI/RI) (hereinafter referred to as “A-CSI”) using the PUSCH.
And, in the downlink, the user data is assigned to a PDSCH and control information is assigned to a PDCCH (Physical Downlink Control CHannel). Downlink control information (DCI) to be transmitted via the PDCCH is classified into a plurality of DCI formats in accordance with the application use and DCI message size (DCI format size). The radio base station apparatus generates downlink control information using a predetermined DCI format in accordance with a communication environment and transmits it to the user terminal.
In the LTE system (Rel-8), there are supported DCI format 0 including an uplink scheduling grant to transmit a PUSCH signal, DCI formats 1/1A to 1D/2/2A/2B including downlink scheduling assignment, and so on (e.g., see Non Patent Literature 2).
The uplink scheduling grant includes uplink shared channel (PUSCH) resource indication, transport format, HARQ (Hybrid Automatic Repeat reQuest) related information and so on. The downlink scheduling assignment includes downlink shared channel (PDSCH) resource indication, transport format, HARQ information, control information regarding spatial multiplexing (where available) and so on. And, the uplink scheduling grant also includes a power control command for PUSCH.